Liquid–solid phase equilibria in metal-rich Hf–Ti–Si alloys

Abstract

Abstract A range of metal-rich Hf – Ti – Si alloys with Si concentrations up to 35.0 at.% was directionally solidified. Liquid – solid phase equilibria in these alloys have been investigated using scanning electron microscopy, X-ray diffraction, and electron beam microprobe analysis. Four phases were identified: (Hf, Ti)5Si3, Hf(Ti)2Si, β(Hf, Ti, Si), and α(Hf, Ti, Si). Microstructural and microchemical evidence provided a clear definition of the Hf – Ti – Si liquidus surface at the metal-rich end and indicated the existence of the invariant reaction: Liquid + Hf(Ti)2Si → (Hf, Ti)5Si3 + β(Hf, Ti, Si) This invariant reaction occurs at a composition of approximately Ti-50Hf-9.5Si, and at a temperature of ∼1420 °C.